Fluid flow systems or assemblies that are pre-sterilized and/or pre-assembled are used in a wide variety of medical and non-medical applications. Medical applications may include, for example, administration of medical fluids to a patient for therapeutic and/or diagnostic purposes, blood and/or blood component or other cell collection or processing, dialysis and other medical procedures. Non-medical applications for such systems or assemblies may include, for example, pharmaceutical or medical device manufacturing and/or cell processing. In the medical field in particular, fluid flow systems or assemblies commonly employ one or more pre-filled containers or other sources of medical fluid or agent and an associated fluid flow circuit or system (sometimes called a tubing set) containing the necessary flow tubing, valves, flow controllers, process chambers and the like to carry out the particular procedure, either alone or in cooperation with a reusable controller or other device. It is not unusual, for example, for a medical fluid flow system to include or be used in association with a container of a suitable drug, saline, anticoagulant, dextrose solution, sterile water, cell preservative or the like, to name just a few examples.
Such a fluid flow system can, however, pose manufacturing or assembly challenges for different reasons. One reason can be that the pre-filled containers of medical liquid, powder or other agent that is administered to the patient or otherwise employed in the medical fluid flow system, require different sterilization techniques than other portions of the fluid flow system. For example, empty plastic tubing, containers, flow control devices and/or processing devices or chambers, which do not contain any substantial amount of liquid or other agent, may be sterilized with gamma or electron beam (e-beam) radiation or by exposure to a sterilizing gas, e.g., ethylene oxide. However, gas sterilization would be ineffective to sterilize an agent, such as a liquid, powder or drug, contained in a sealed container, and exposing the agent to ionizing radiation may degrade or otherwise have a deleterious effect on the agent. Also, there may be situations where different portions of a sterile fluid flow system, even though suitable for the same sterilization process, are separately manufactured and sterilized for other reasons and then subsequently assembled in a sterile manner.
In addition sterile connections often need to be made on site, by the end user, e.g., at the location where the fluid flow systems are being used to treat patients or collect or process blood, or blood components, or biologic materials, or in other therapeutic or diagnostic procedures. For example, it may be desired to join a fluid source, filters, tubing or the like to other apparatus without comprising the sterility of any pre-sterilized components or parts of the assembly.
As a result of these various needs, a number of different approaches have been used in assembling sterile fluid flow systems or making sterile connections. One recent development in sterile connection systems and methods is described in U.S. Provisional Patent Application Ser. Nos. 61/578,690, filed Dec. 21, 2011; 61/585,467, filed Jan. 11, 2012; and 61/617,745, filed Mar. 30, 2012; and in PCT international application no. PCT/US2012/069103 filed Dec. 12, 2012, each of which is hereby incorporated by reference in its entirety. One example of a fluid flow circuit or subassembly employing a sterile connection system described in these applications includes a fluid conduit including at least one open end terminating in a heat meltable end material (e.g., a thermoplastic material) and a sealing member sealing the open end of the conduit. The sealing member includes at least one heating element configured to melt the end material upon energizing. Upon heating, the sealing member and open end of the conduit are relatively movable to expose the molten end material. Two such fluid flow circuits or subassemblies may be joined in a sterile manner to form a fluid flow circuit assembly by simultaneously melting the thermoplastic material of the open ends (by heating the heating element), relatively moving the sealing members and the respective open ends to which they are sealed to expose the open ends, and bringing the exposed open ends together while melted to form a junction between the fluid flow circuits that allows fluid flow therebetween.
Various thermoplastic materials have been identified for use in the above development, including polypropylene. Polypropylene, however, does not bond as well as desired to polyvinylchloride, which is a common material in fluid flow circuits. Accordingly, alternate materials and sealing and bonding conditions still need investigation and characterization.